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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

446

HARDENED  OR HYDROGENISED  OILS

Examples of the characters of blown oils in comparison with those of
the corresponding original oils, are as follows :


	Specific gravity
	Zeiss butyro-refracto-
	Saponili-
	Iodine
	Hydroxy-acids insoluble


	at 15.
	l meter Number
	Number.
	Number.
	in petroleum


	
	at 15.
	
	
	Aether, %.

.., ,       .,           (ordinary   . Colza oil          \ , ,         J (blown .
	0-912-0 -91 7 o -967-0 -977
	68-69 80
	l 70-181: 197-268
	94-106 46-65
	0
 20-28

  , ,          ,    ., ( ordinary   .
	0-922-0-925
	68
	191-198
	107-110
	o

(blown .
	0-972-0-979
	80-81
	213-226
	50-66
	26-20

,..,,.,      (ordinary  . Ox-foot oil      \ , ,         J
	0-921
	62
	1 94
	71
	__

(blown .
	o -972
	73-74
	241-242
	^
	

Fish oil            {ordinary   .
	o-925
	78
	IQO-1QI
	134
	__

(blown .
	0-980-0-985
	90-91
	247-248
	73-74
	

HARDENED   OR  HYDROGENISED   OILS

These are obtained by subjecting liquid fatty oils, either vegetable or
animal, to the action of hydrogen at a temperature of 130-140 in presence
of a catalytic substance, usually finely divided reduced nickel, or palladium,
platinum and various metallic oxides. The unsaturated liquid fatty acids
(oleic, linoleic, etc.) of the glycerides of the oils are transformed into solid
stearic acid, so that the oils themselves become solid.

These products, marketed under the names of Talgol, Candelite, Coryphol,
are usually obtained by hydrogenising marine animal oils (in particular,
whale oil), but they may also be prepared from vegetable oils (cottonseed,
soja-bean, castor, etc.).

As a rule, hardened fats are solid and of the consistency of tallow (with
very prolonged hydrogenation they acquire the hardness of waxes) and
they have persistent colours, odours and tastes which are similar to those
of tallow but no longer recall the original oils. They usually melt at 40-50,
but the strongly hydrogenised ones have still higher melting points. Their
fatty acids melt at temperatures 2-3 below the points of fusion of the
neutral fats. Their acid number is small and their saponification number
normal (190-195), while the iodine number depends on the degree of hydro-
genation and may fall to a few units.

Hydrogenised oils give the general colour reactions of the original oils
very similarly to the latter : thus, they give Hauchecorne's, Heydenreich's
and Bellier's reactions if they are derived from vegetable oils and Tortelli
and Jaffe's reaction if from marine animal oils. They do not, however
give Halphen's octabromide reaction for marine animal oils (see p. 428) or
Halphen and Milliau's reactions for cottonseed oil; but partially hydro-
genised cottonseed oil, even when solid, still gives Halphen's reaction quite
distinctly.

Hydrogenised oils contain unchanged the unsaponifiable substancesife. When mixed with zinc white or minium, it should dry completely within